irrational

not based on, or not using, clear logical thoughtsynonymunreasonablean irrational fearYou're being irrational.oppositerationalWord Originlate Middle English: from Latinirrationalis, from in-

‘not’

+ rationalis (from ratio(n-)

‘reckoning, reason’

, from rat-

‘reckoned’

, from the verb reri).Extra examplesThere was nothing inherently irrational in such a decision.These are just irrational fears.What is the reason for this seemingly irrational behaviour?You’re being irrational.